Geochemical Characteristics Of Ore-bearing Rocks And Genesis Of Tuwudong Copper Deposit,Eastern Tianshan

The eastern Tianshan,located in the southern margin of the Central Asian Orogenic Belt,is an important ore belt and characteristic by Cu-Au-Mo-Fe-Pb-Zn and other metals mineralization.Tuwudong deposit is located in the middle part of the Dananhu-Tousuquan island arc belt.It is an important achievement of prospecting and exploration in the eastern Tianshan Mountains.Based on field geological and drilling core investigation,micro observation,whole rock geochemistry and Sr-Nd isotopic analysis,sulfur and lead isotopic studies of sulfide and ore-bearing rocks,and Re-Os dating of molybdenite,combining with previous data.The main achievements of this study are as follows:1.Tuwudong hosts in the Carboniferous Qingeshan Group,and the boundary between the orebody and the surrounding rock is not obvious.Its shape presents thick plate and stratoid.The ore-bearing rocks of Tuwudong deposit in the study area are plagioclase granite porphyry and diorite porphyrite.According to the mineral symbiosis combination and the crosscut relationship of vein bodies,the mineralization process of the Tuwudong copper deposit can be divided into four metallogenic stages:stage I quartz + magnetite + chalcopyrite + pyrite,stage ? quartz + bornite +chalcopyrite + pyrite + epidote,stage III quartz + molybdenite + chalcopyrite +pyrite,and stage IV epidote ± chlorite ± pyrite.2.Geochemical data show that the plagiogranite porphyry,diorite porphyry and quartz porphyry in the Tuwudong porphyry copper deposit are all enriched in K,Rb,Sr,Ba and other large ion lithosphile elements,and relatively depleted in,high field strength elements such as Nb,Ta,Ti and Th.Diorite porphyry has the characteristics of island arc volcanic rocks,and the plagioclase granite porphyry and quartz porphyry have the characteristics of adakitic rocks.3.The whole rock geochemistry and Sr-Nd isotope analysis suggest that the plagiogranite porphyry in the study area is typical of adakite,and` it was mainly sourced from the partial melting of the subducting oceanic crust.The diorite porphyrite originated from the partial melting of the subducted slab beneath the Dananhu-Tousuquan island arc.4.The Re-Os isochronous age of the Tuwudong molybdenite deposit is335.6±4.1 Ma,which shows that copper mineralization is closely related to the acidic magmatism of the Carboniferous period in this area,indicating that the Tuwudong copper deposit was formed in the Carboniferous subduction island arc environment.